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The TEMS Study of the Economic Impact of the Purple Line: A Good Example of a Badly Flawed Report

A review of a recently released report, purportedly on the economic impact of the Purple Line, should be of interest not only to those with a direct interest in the Purple Line project itself, but also to those interested in how such work is now used as part of a political process to influence decisions on major public projects. It is a badly flawed report. Nonetheless, its results were announced with great fanfare, and treated without question by news organizations such as the Washington Post.

The Purple Line is a proposed light rail line which would run in a 16 mile arc through suburban Washington, DC, from east of the city to its north. It is a controversial project, due to its high financial as well as environmental costs while serving relatively few riders.

An earlier analysis on this blog calculated that the full cost per trip on the proposed system would be an estimated $10.42 (and double this per day for a round-trip). But the system would take in only 38 cents in average additional fares per trip (since a large share of the riders will be free or reduced rate transfers from the bus or existing rail systems), leading to a subsidy of over $10 per ride. And this analysis assumes that the current cost and ridership projections will hold true. Such projections have generally proven to be highly optimistic on other light rail projects.

Despite the high cost, there are significant vested interests pushing strongly for the project. In particular, land developers along the proposed corridor would see the value of their properties rise, possibly by the hundreds of millions of dollars. And local government authorities (in particular those of Montgomery and Prince George’s Counties) have come out in favor: Almost all of the cost would be borne by the State of Maryland or the Federal Government, and the subsidy payments from the State of Maryland would be locked in (under the proposed PPP contract) for 30 years beyond the estimated 5 year construction period.

There are numerous and major flaws with the report. This blog post will go through some of the more important ones. But first it will summarize several of the red flags that should have signaled to any serious analyst and news organization that there could be problems with the report, and that a more careful reading would have been warranted before its conclusions were widely publicized.

A number of the problems with the report are quite technical. I would not suggest that a general news reporter would have the technical knowledge necessary to have discovered these himself or herself. But the red flags are obvious, and should have signaled to the journalist that there could very well be issues here, and that if he did not have the skills to assess the report, then he should have consulted with some neutral third party to do such an assessment for him. The Purple Line project is controversial, and an experienced reporter and news organization should have recognized that a report such as this, commissioned by and released by advocates for the project, may not be one to take on faith. But this was not done.

B. Red Flags

Some obvious issues should have raised attention:

1) Gigantic Returns: The TEMS report concludes that building the Purple Line will lead to an “Increase in income to local households of $2.2 billion per year” (Chapter 8, Conclusion). This is astounding. The cost estimate to build the line used in the study (from the August 2013 Final Environmental Impact Study) was only $1.9 billion (expressed in 2014 prices). (Note: The most recently published estimate, from November 2014, puts the expected cost a good deal higher, at $2.45 billion in current dollars, or about $2.3 billion in terms of 2014 prices. But the TEMS study used the earlier cost estimate.)

A $2.2 billion increase in annual incomes on a one-time $1.9 billion cost implies an annual rate of return of 116%! One is generally content with annual rates of return of perhaps 16%, or even 10%, on public projects. Yet this one claims a return of 116%. This should have been an immediate flag that something is questionable in what was done. As the adage goes, if something is too good to be true, it probably is.

2) Implausibly Precise Statistical Results: While a more technical issue, any observer conversant with basic statistics and regression analysis would have been surprised to see that the t-statistic was as high as 250 in the cross-section regressions in the simple model of travel demand (Exhibit 4.2 of Chapter 4). The t-statistic is a measure of how tight the data fits around the estimated coefficients of a regression equation. Any t-statistic greater than 2.0 is generally taken to imply the coefficient is statistically different from zero (with a 95% confidence). In cross-section regressions, one is normally happy to find t-statistics of 2 or 3. But in the statistical regression reported on here, for the estimated number of trips by commuters between two geographic zones as a function of just two simple variables, the t-statistics varied between 200 and 250.

Such precision in results in statistical work such as this is highly surprising. In the real world there are many other determinants of travel demand between two zones than just the two variables used in the TEMS study (one for the cost of such travel, and one a constructed variable based on population, incomes, and employment). While I do not have access to the data they used to determine what is going on, any statistician would be highly suspicious of such precise results.

3) Who Sponsored and Paid for the Report: An assessment of any report such as this starts with finding out who commissioned and paid for it. The Washington Post article and editorial both state that the report was commissioned by Montgomery and Prince George’s Counties, the two Maryland counties through which the Purple Line will run. No one else was mentioned. Yet a report on the same presentation that day by the Gazette (a local newspaper of Suburban Maryland) noted that the Greater Washington Board of Trade was also a commissioner of the work, along with the two counties. The Board of Trade is an industry group, whose members include construction companies and property developers, a number of whom will benefit directly if Maryland proceeds with this project.

Good journalism would have called for full disclosure on who sponsored and paid for the report. If this was misunderstood at the time, a correction should have been reported later. And an obvious question at the presentation of the report would have addressed not only who commissioned the report, but also what was the total cost and how was that cost shared among the sponsors. Given the tight budgetary situation of all governments these days, it would not be surprising if a disproportionate share of the costs came from the Board of Trade (and some sub-set of its members who might have an interest in the outcome).

C. Problems With the Report

Once one delves into the details of the work done, a number of flaws become clear. This section will summarize a few of them. The sequence followed is that of the report, starting with the theoretical construct, through the statistical work, and then the results. However, this sequence unfortunately means that the more important issues are the ones further down on the list, rather than at the top. I hope the reader will be patient.

1) Confusion in the Theoretical Framework: There are two major parts to the report. The first seeks to estimate what it terms to be the long-term supply side impacts of the project, while the goal of the second is to estimate the immediate impacts on the region from the construction spending itself. We will focus first on the report’s supply side analysis, starting with the theoretical framework presented. A separate section below will review how the immediate impacts were estimated.

The report provides an elaborate theoretical framework (in Chapter 2) for the approach they say they are taking, but there are issues. It starts by saying they will work through a supply side analysis to determine how a transportation investment such as the Purple Line will increase productivity and output, and assert that this will be equivalent to (the “mirror image” of) the more traditional approach of valuing transportation investments by how much cost and time they save for drivers and riders. But in fact this will not be the case. Measured levels of household incomes simply do not include as one element the time saved (or as a negative, the time consumed) in travel. Yet the TEMS report uses the standard measures of household incomes and other such economic variables in their statistical work. Thus the TEMS approach and the traditional approach of valuing the benefits from transportation investments will not be mirror images of each other. They will produce totally different results.

They also define what they call “economic rent”, to be a function of the variables: population structures, industrial structures, education levels, cultural characteristics, and “transportation efficiency”. They do not further define the five variables other than transportation efficiency, but argue that they will be largely unchanged over a period of 10 to 20 years or so. Thus any changes over such a period will only be due to changes in transportation efficiency. Actually, this will not be the case, as any geographic area will see its population and incomes changing over time. But while incorrect, it should not matter to their analysis. One could interpret their approach as looking for the partial effect of transportation efficiency on what they call economic rents.

But there are problems with how this is implemented. First, they take as their measure of “transport efficiency” a weighted average cost of automobile travel (for both time and financial costs) from a specific geographic zone to all other geographic zones in the region. Why they should include only automobile travel in a study looking at the impacts of a light rail line is not clear. But more of a concern is that “economic rent” is measured by a series of what they call “proxies” (specifically: employment, household income density, and residential property value density), and that they assume that each of these variables is separately a function of transportation costs (and transportation costs alone).

This is a simplistic framework. It is not at all clear why the specific variables they define as “proxies” for economic rent do indeed capture what economic rent really is. They merely assert they do. Economic rent corresponds to the value of land in a particular location. Land rent, with all else equal, will generally be higher in more central locations with lower transportation costs. But land rent is not synonymous with employment or with household incomes, for example. Thus while there may well be a relationship between land rents and transportation costs, it is not at all clear why there should be the same such relationship between household incomes and transportation costs.

There are therefore issues with the theoretical framework used.

2) Flawed Statistical Analysis: I noted above that at least certain of their statistical results appear to be too good to be true. But there are other issues as well.

One mistake is to assume that a relationship that might apply at a broad geographic scale will apply in the same way in a more limited jurisdiction. Their basic statistical work is based on an analysis of the relationship between their socio-economic proxies and average transportation costs over a set of 299 geographic zones in the Washington and Baltimore metropolitan areas. This is a large area, stretching from the Pennsylvania border to south of Fredericksburg, Virginia (a distance of over 150 miles), and from the Shenandoah Valley in Virginia to the Chesapeake Bay.

Distances such as this matter a good deal in deciding where to live and commute. There will not be many people commuting from Fredericksburg to Baltimore and beyond, or from Warrenton to Annapolis. Even if one found a nice house and neighborhood in such areas, the cost of commuting will dominate in the decision not to live there. And a statistical regression, when properly done, should pick up such relationships and show that the commuting costs of course matter.

But there is then a problem is assuming that the same statistical relationship will apply similarly, and with the same parameters, when examining housing and commuting choices on a much smaller scale. If your commute would be five miles, say, from one possible home location, and seven miles from another, the difference in commuting times might not be all that important. Rather, one might choose the location that is further away based on how much one likes the specific house or neighborhood, where your friends live, and other such factors. It would be a mistake to assume the statistical relationship with transportation costs will be the same.

Yet the authors of this report do assume this. They assume that the relationship they estimate based on the region wide data stretching over 150 miles and many hours of potential commuting time will apply similarly at the scale relevant to riders deciding whether or not to take the Purple Line. The Purple Line will only be relevant to largely local riders, living and/or working within a few miles of the 16 mile long rail line. Statistically, the authors made the mistake of presuming that relationships in a data set that is largely “out-of-sample” will apply similarly in the more limited scale relevant to the Purple Line.

There are other issues as well. As already noted, the t-statistics for their travel demand model estimations are implausibly high. It is also odd that the estimated slope coefficients in their regressions relating employment, household income density, and property value density (in Exhibit 5.4), and later housing density and housing units density (in Exhibit 5.7), as a function of average transportation costs, are all in the relatively narrow range of -3.30 to -3.97. By the way the equations were structured, these coefficients are all what economists call “elasticities”, meaning that a 1% decrease in average transportation costs in the zone will lead to increases of between 3.30% and 3.97% in the various socio-economic variables. It is surprising that these response rates are all so close to each other, for such very different variables as employment, household income densities, property values, and so on. While I cannot say what might be causing this without knowing more on precisely what was done, the similarity in response rates over such disparate variables is probably a flag that something was not done properly in the statistics.

There is also a, possibly related, technical statistical issue in that they assume in one set of relationships that their socio-economic measures (income, etc.) are a function just of their average transportation cost figures (equation 12), while in another equation (equation 6) they postulate that travel demand will be a function of certain constructed socio-economic variables (which are themselves built up from the basic set of socio-economic variables) and average transportation costs. This implies in their system that the variables they are using (the socio-economic variables and average transportation costs) to explain travel demand are not in fact independent of each other. When this is the case, ordinary least squares regressions will not work, and one needs to utilize a more sophisticated statistical approach.

3) The Elasticity Estimates Are Just Not Plausible: While the similarity across the elasticity estimates is curious, it is more important to recognize the implications of the values themselves.

Using the case of the response of household income density to transportation costs, the equation the TEMS study estimated found an elasticity of -3.79. That is, for a 1% fall in transportation costs in the area, household income density will rise by 3.79%. Some of this might come from higher average household incomes in the area and some by more homes being built in the area, both of which will increase the income of the area.

This would be a huge response, if true. Transportation costs (private plus intracity public transit) on average accounts for about 15% of the consumer price index (BLS data on the CPI weights). Median household income along the Purple Line is roughly $80,000 (based on a simple average of the median household incomes at the four major stations where there are now regular MetroRail lines). 15% of $80,000 is $12,000 spent directly on transportation costs. To this one should add the value of time spent commuting (as an additional cost). Based ultimately on Census Bureau data, a study found that residents of Washington, DC, spend an additional 11% of their working hours each week on commuting. Applying this 11% to the $80,000 median household income, the total cost of transportation for an average household is 26% of $80,000, or $20,800.

The TEMS regression results, if they are to be believed, imply that a 1% reduction in transportation costs ($208 = 1% x $20,800) will lead to a 3.79% rise in household incomes ($3,032 = 3.79% x $80,000) through either a rise in per household incomes or in the number of households in the zone or by some combination. This implies that a subsidy of just $208 per household for what they spend on transportation will lead to a rise in household incomes in the area by $3,032!

This would be amazing, if true. A small $208 cost would be converted into more than a $3,000 gain in annual incomes! And with government income tax rates averaging roughly 25% (the figure the TEMS study uses), the government tax take would rise by over $750. Only 28% of this increase in the tax take could then be used to pay for a further $208 subsidy, and one would have the equivalent of a perpetual motion machine (or in this case a perpetual wealth machine).

Unfortunately, it is not likely that there will be such a response to transportation investments. Perpetual wealth machines do not exist. The parameter estimates are simply implausible. The reason why the result may have been found (assuming the statistics was done properly, which is itself not clear) will be discussed immediately below. The implausible parameter values also explains why the TEMS study found such purported high returns (of 116% a year) for an investment as costly and as inefficient as the Purple Line. But as the next section will discuss, the interpretation was wrong.

4) Lower Transportation Cost Is Not the Main Cause of Higher Incomes – Correlation Is Not Causation: The regression equations summarized in Exhibits 5.4 and 5.7, regress variables such as employment, household income density, and so on, on average transportation costs in the zone. But it is a well known principle in regression analysis that such regressions do not demonstrate causation. Rather, they can only show correlation.

Nevertheless, the TEMS report asserts that the correlations found in their regressions do show that employment, household income density, and so on, will rise as a direct result of average transportation costs falling. The percentage rise will be in accordance with the elasticities estimated, they assert, and will be a consequence of the higher productivity of the economy that lower transportation costs leads to.

But it is not at all clear that the causation goes in the direction the TEMS report asserts. The correlations may rather be showing that people with high incomes prefer to live in areas where transportation costs (and commuting times, which are part of transportation costs) are relatively low. In the Washington, DC, area, to take an example, the Georgetown neighborhood is a high income area in the city, close to the central downtown office zone, and hence an area with relatively low transportation costs. Many rich people who can afford it like to live in the area, and home prices are high reflecting this preference. But the residents of Georgetown did not become rich because transportation costs are on average relatively low there. Rather, rich people have sought to live in Georgetown for, among other reasons, the relatively low cost of getting to work from there.

Thus one finds in the regression results a correlation between high incomes (and the other variables estimated) and relatively low average transportation costs. But the residents did not become rich as a result of some reduction in transportation costs. They were already rich, which allowed them to move into an area such as Georgetown.

Thus it is incorrect to conclude, as the TEMS study does (see the beginning of Chapter 6, page 36), that building the Purple Line will “create more than 27 thousand jobs; will increase property value (sic) by 12.8 $ billion (sic) and the household income (sic again) is estimated to increase by $2.2 billion”. Building a rail line (or any other transportation improvement) will not itself raise household incomes in such a way or create thousands of jobs. Rather, the correlation observed (and assuming the statistical analysis was done correctly) can arise due to the choices people make between living in one neighborhood and another.

Note also that a decision of a relatively high income households to move to a location such as Georgetown in preference to a location further away from their job, will lead not only to higher income households concentrating in Georgetown, but to a symmetrical reduction in such households in the other locations they chose not to move to. Similarly for property values: Home prices will be bid up in Georgetown, and will see a reduction relative to what they would otherwise be in other locations. But this is arising not because lower transportation costs is making people richer in Georgetown (that is, not due to a supply side effect increasing productivity, as the TEMS study asserts), but due to shifts in location preferences.

This is important. A reduction in transportation costs is not making the region richer through some supply side effect, and certainly not in accordance with regression coefficients such as those found (with an elasticity of -3.79 for income, for example). Rather, the regression equations (and assuming again that the statistics were done properly, even though there are questions on that) are picking up at best a locational preference that shifts households from one location to another, and has limited or no effect on household incomes or property values in the region as a whole.

5) The Multiplier Analysis Fails on Several Counts: In addition to the “supply side” analysis reviewed above, the TEMS study undertook to estimate the immediate impact on employment and incomes in the areas immediately surrounding the Purple Line corridor during the construction period. It was this analysis that led to the stated figure in the news reports that the project would create 4,000 jobs per year during the construction period (see here and here for example).

The multiplier analysis is decidedly not supply side analysis, but rather a purely demand side assessment of how much incomes and jobs would rise to produce what goes into the project. And in a multiplier analysis, one takes into account not only what is used directly in the project, but also the production of the inputs that go into what is used directly and then the inputs into the inputs, and so on.

When unemployment is high and factories are underutilized, a multiplier analysis can be of interest. An earlier post on this blog discussed what the fiscal multiplier means at the national level, and how the value of the multiplier will differ across countries and under different conditions, in particular whether one is assessing the multiplier at a time of high unemployment or low. It can certainly be a useful tool if properly applied. But one needs to be careful in how it is applied, and here the TEMS study fails.

There are multiple issues:

a) The TEMS study failed to recognize that the major share of the inputs to the project will come from outside the region: The expenditures that are the basis for the multiplier analysis come from the FEIS, which was finalized in August 2013. The FEIS study has the capital cost figures in 2012$, and the TEMS authors puts them into 2014$. The capital cost estimate in the FEIS would then be $1.9 billion in 2014$ (it is now projected to be higher). From this, the TEMS authors subtracted the cost of the train vehicles of $0.2 billion, as these vehicles would be built somewhere outside the Washington, DC, metropolitan region (the initial set of streetcar / light rail line vehicles purchased for a new line in Washington, DC, indeed came from the Czech Republic). Thus building such cars would have no multiplier effects here. This was correct.

But then the TEMS study assumed that the entire remaining $1.7 billion would be used to purchase items for the Purple Line from production in Montgomery County, Prince George’s Country, or Washington, DC. This is of course not true. There are no steel mills in Washington, DC, or its Maryland suburbs that produce steel rails. There are no plants that produce the sophisticated electronics that goes into the communications and other systems of the control centers (Siemens of Germany is one of the main global suppliers of such systems). The overhead power lines are not made from copper and other materials mined locally. And so on. The primary and perhaps sole local component would be the share of the $1.7 billion paid to local labor for the installation. This will be a significant cost item, of course, but far less than the full $1.7 billion.

It is thus a gross error to have assumed that the purchase of the steel rails, the communications equipment, the overhead power lines, and much of the rest, will lead to local multiplier impacts in the Washington region from their production. Their production is elsewhere. Thus the true multiplier impacts in the Washington region, even if one accepts their methodology, will be nowhere close to those they estimate.

But it gets worse.

b) The Construction Cost Estimates Were Triple-Counted, Once Each for Montgomery County, Prince George’s County, and for Washington, DC: The TEMS study concluded that there would be an additional $7.0 billion in gross regional product as a consequence of the $1.7 billion in construction expenditure for the Purple Line. This implies a multiplier of 4.1 (= $7.0 billion / $1.7 billion). Such a multiplier would be huge. At the national level, one might expect a multiplier of 2 to 3 when unemployment is high, and many economists have argued that it might be more like 1.5. It really depends on the degree of unemployment and other conditions. But no one says it will be more than 4.

Furthermore, the multiplier at the national level will be much higher than the multiplier at a regional level. If my income goes up due to employment on some project, I will spend that income not only on goods and services produced in the immediate Washington, DC, region, but also on pork from Iowa, wines from California, vegetables from Florida, cars from Michigan (or Germany), and so on. Hence the local multiplier will be far below what it will be at the national level, and will be smaller the smaller one defines the local region (less for the city of Washington, DC, than for the Washington, DC, metropolitan region, for example).

So how did the TEMS authors arrive at such a high multiplier of 4.1? They made a big blunder. Examination of the tables showing their calculated Gross Regional Product figures for Montgomery County, Prince George’s County, and Washington, DC (Exhibits 7.10, 7.11, and 7.12) shows increased construction sector product of $1.66 billion in each case. But this is (to three significant digits) the estimated total construction expenditure assumed for the Purple Line (the $1.7 billion figure is rounded from a more precise figure of $1.656 billion that one can obtain by reproducing the process they followed to arrive at their $1.7 billion). The individual figures for Montgomery County, Prince George’s County, and Washington, DC, differ very slightly (in the fourth digit) since the feedback effects in the input-output matrices used for the multiplier analysis will differ a bit across these jurisdictions.

The TEMS authors triple counted the expenditures on the Purple Line. Not only did they assume the entire $1.7 billion non-vehicle cost of the line would be spent locally, but they presented figures based on $1.7 billion being spent in Montgomery County, $1.7 billion being spent again in Prince George’s County, and $1.7 billion being spent again in Washington, DC (and the Purple Line will not even touch Washington).

The results for the multiplier analysis are therefore completely wrong, even if one takes their methodology for granted. They made a big blunder. But what is perhaps even more worrying is that the multiplier they reported of 4.1 was clearly far too high for what one would expect in any such analysis at a regional level. Despite what should have been a big flag that something was amiss, the results were reported without the authors reviewing how they had arrived at such a large and implausible number.

c) The Multiplier Methodology is Mechanical, and Implies That Cost Overruns are Good: Finally, one should note that a multiplier methodology such as that used here, even if applied without the mistakes that were made, is a mechanical one. One takes construction expenditures, at whatever level they are, and multiplies out the implied levels of employment, regional product, and personal incomes that follow based on this multiplier approach.

An implication of this is that every time the cost goes up, the calculated “benefits” rise also. Indeed, under a multiplier analysis such as that done here, the benefits will rise in proportion. If the project ends up costing twice as much, then the “benefits” in terms of higher jobs and incomes will be twice as much. But this is of course silly. Cost overruns are not good.

The problem is that the wrong question is being asked. A project is not a good one because it requires more (rather than less) labor to build it. Higher costs are not a good thing. Rather, the objective of a transportation investment is to provide transportation services, and the question that should be asked is what is the lowest cost and most efficient way to provide those services. If one can achieve the transportation aims with a project that only costs half as much, then one should follow that approach rather than the more expensive one. And if one then has additional budget resources available through following the lower cost approach, one can then consider undertaking other projects, for transportation or whatever. In the end, the number of jobs involved will be similar if similar amounts are spent.

6) The most basic flaw in the TEMS study was that it was asking the wrong question: The question the TEMS study sought to address was what the economic impacts would be of building this project compared to doing nothing. But this was the wrong question.

No one is advocating that nothing should be done to address the very real transit issues in the area of the Purple Line corridor. The issue, rather, is how best to address the transit needs. Any assessment of the Purple Line should not be relative to doing nothing, but rather relative to what the best other alternative would be. If the best other alternative is superior to the Purple Line, then the actual impact of building the Purple Line (instead of the alternative) is negative.

The Alternatives Analysis / Draft Environmental Impact Statement (AA/DEIS), did look at a number of bus alternatives. All turned out to be far cheaper than light rail both in total amount and per rider (see Summary Table 6-2 of Chapter 6 of the AA/DEIS). The most cost effective (in terms of cost per new rider) was a simple upgrade of the regular bus system, with a cost per new rider that was 60% less than the light rail alternative chosen. Furthermore, a bus system can be easily scaled up or down, with frequency and routes adjusted depending on ridership and changing development patterns. A light rail system is fixed, and fixed forever. It is also basically either all the way on or all the way off. There is little flexibility.

It should also be noted that the true alternative should have recognized that not just buses provide transit to riders in this corridor. One also has the existing MetroRail system. The four larger stations of the Purple Line would be at intersections with four MetroRail stations, and existing MetroRail service would often require less time for the journey than the Purple Line would. Light rail lines are slow. For example, the FEIS highlights (see Table 9-1 of Chapter 9 of the FEIS) that in the year 2040, a bus journey from Bethesda to New Carrollton (the two end points on the Purple Line) would require 108 minutes, while the Purple Line light rail would require 63 minutes, a saving of 42% they state. But the FEIS failed to recognize that no rational person would take the Purple Line for such a journey, since one could make the same trip by MetroRail (today and in 2040) in just 51 minutes. The Purple Line would take substantially longer for this journey than simply taking the existing MetroRail service. Nevertheless, having failed to take into account the MetroRail alternative, the FEIS (and then the TEMS study as well) calculated benefits as if a transit rider would save 45 minutes ( =108 – 63) from Bethesda to New Carrollton by taking the Purple Line rather than the “no build” alternative of a bus following the same route.

The alternative considered in the FEIS to the light rail line was therefore a straw man. They did not take into account the MetroRail alternative, which would be as fast or faster for many of the riders, nor did they consider seriously what an upgraded bus system could do. And much could be done to upgrade bus service from the second class system it has been treated as, through use of a combination of redesigned routes, express routes on some corridors, perhaps bus rapid transit on some routes, and more. But even the straw man they did consider was far more cost effective than the light rail alternative chosen.

D. Conclusion

There are major flaws in the TEMS study, both in its structure and in its implementation. Some are outright blunders, such as the triple counting in the multiplier analysis by treating the Purple Line as if it were to be built completely in Montgomery County, completely again in Prince George’s County, and completely again in Washington, DC. But even without such mistakes, the approach taken has major issues, such as from confusing correlation with causation, failure to recognize that the bulk of the inputs would come from elsewhere, the statistical issues, and more.

While a number of the issues are technical, there were also easy to spot clear red flags that something was wrong. A public project such as this does not generate an annual rate of return of 116%. One does not get fantastically precise statistical results with real world data. These and other results should have served as flags first to the authors of the study that something was wrong, second as a warning to those commissioning the study that the results looked odd, and third as a signal to the journalists covering the release that they should consult with some neutral third party who would have the necessary expertise to advise on whether there might be issues. When something looks too good to be true, it usually is.

But such a review was not done, and the results were announced as if they were valid.